The present invention relates to tires. In particular, it concerns the mounting and demounting of a tire casing on and off a rim, and it also concerns, consequently, the mounting and demounting of tire casings on a vehicle, for example, for their replacement.
It is known that the development of wheels equipped with tires has led to a trend in design which, at present, consists of making the wheel easily demountable from the vehicle, the tire being removable from the wheel in an operation carried out at the shop with specialized machines. As is well known, the wheel is demountable from the hub of a vehicle usually by unscrewing a set of bolts. The wheels, the rims and the beads of a tire casing are covered by manufacturing standards which dictate the outer shapes and dimensions of those parts (see, for example, the ETRTO in Europe).
Most wheel and tire assemblies are made according to the principle just mentioned. This is the case with almost all equipment for passenger vehicles. It is also the case with most equipment for trucks, construction machinery, fanning or logging equipment, etc. As far as the largest dimensions are concerned, for example, to equip construction machinery or earth movers, the assemblies are built according to comparable principles, except that the rim is generally made in several parts assembled by a large number of bolts. This corresponds to a tire casing section having the general appearance of a horseshoe (xe2x80x9cxcexa9xe2x80x9d) open on the side of the axis of rotation of the tire, which proves simpler to manufacture than other types of sections (see, for example, the closed toroidal tire); the manufacturing facilities available have been developed and optimized for this type of tire. The open xe2x80x9cxcexa9xe2x80x9d shape is also appreciated because it makes it possible to inspect the inside of the casing and affords access to the inside of the casing in order to repair it, if necessary.
The present state of the art is the result of a technological evolution which, in the course of time, has been directed at offering tire and wheel assemblies which are as easy as possible to mount on and demount from the vehicle. Thus, the solution proposed for passenger vehicles makes possible the removal of the wheel and tire assembly from the hub simply enough to be within the ability of the ultimate user.
There have been very few technological developments in the course of the past decades concerning the principle of mounting a tire casing on the wheel and the principle of mounting the wheel on a vehicle. In some specific applications, such as wheel and tire assemblies for racing cars (like the Formula 1), in order to be able to mount and demount the equipment as quickly as possible, a center attachment wheel is used, making it possible to fasten the wheel to the hub of the vehicle very rapidly. But this type of fastening requires the use of very specific tightening and loosening wrenches, which are not available in most machine shops. The problem of wheel and tire equipment mounting and demounting time also arises for truck fleets or for construction equipment.
In the course of the specification, the expression xe2x80x9ctire casingxe2x80x9d is reserved for the object having two sidewalls attached to a crown part having a tread, the two sidewalls each ending radially inward in a bead. This is the commercial product as commonly manufactured nowadays. The part indeformable to working stresses, on which the tire casing is mounted, is called a xe2x80x9crimxe2x80x9d, the beads serving to position the tire on the seats of a rim. A xe2x80x9cwheelxe2x80x9d includes a rim and the means for mounting that rim on a hub, which is, for example, usually a wheel disk. As used herein, a xe2x80x9ctirexe2x80x9d is an assembly constituting a toroid delimiting a tight chamber that can be inflated to the normal working pressure provided for by the designer. A tire casing mounted on the rim is one of the possible ways of making a tire (in the meaning given to the word xe2x80x9ctirexe2x80x9d hereabove).
However it is made, the mounting of a tire casing on a rim consists of positioning the beads on the rim seats and against the rim flanges. Each rim seat requires centering (radially) and generally presents a slight conicity making possible a degree of tightening of the casing, when the bead is axially displaced toward and up to the flange, which requires of it an axial positioning relative to the fastening surface of the wheel on the hub of the vehicle. In other words, the rim seats can be considered positioning the beads relative to the axis of rotation of the rim, while the rim flanges position the bead relative to a reference perpendicular to the axis of rotation of the rim. In addition to the function of imposing a geometrically precise position for the bead of the tire casing, the rim seat and the rim flange also have the function of ensuring tightness between the rim and the tire casing, and have the function of making it possible, through sufficient tightening of the tire on its rim, to transmit a torque between the rim and the tire casing.
The object of the present invention is to simplify radically the mounting and demounting of a tire on and off the vehicle it equips. According to one aspect of the present invention, the mounting and demounting of a tire casing or of a tire on and off the rim supporting it do not necessitate a specialized mounting machine, like those making it possible to have the flange of the rim crossed by the beads of the tire casing, nor the tightening or loosening of a large number of bolts. The invention proposes a solution which makes it possible to fit a tire on a support that it will be convenient to call xe2x80x9crimxe2x80x9d (because it is a support not deformable on working stresses) in a very simple manner: a simple relative transverse displacement between tire and rim suffices, the tire and rim remaining with merged axes during the relative translation movement.
The invention proposes a toroidal tire including, as seen in mounted position on a suitable rim:
a mounting base on the rim, said base forming a sleeve extending crosswise and being capable of forming a closed toroid defining a tight chamber, said base constituting the radially innermost wall of said toroid;
said base being intended to be mounted on the rim; securing means for axially opposing any relative movement of the tire on the rim at least in one of the two directions, said securing means being:
arranged on the radially inner face of the base;
designed to cooperate with a complementary bearing arranged on the rim in order to oppose any relative movement between tire and rim axially in the said direction at least;
arranged in a part of the base which presents a degree of flexibility between a relaxed natural position and a position radially stressed outward, in which those securing means are free of any engagement with the said complementary element, said part of the base and the securing means being so shaped and constituted that, when said chamber is at the same pressure as the atmospheric pressure prevailing outside the chamber, the securing means are engaged with the complementary element, so that the tire will be automatically secured in at least said one direction on the rim, release of the securing means requiring subjecting the latter to the action of outside means serving to make said securing means take said position stressed radially outward.
Depending on the applications, the xe2x80x9csecuring meansxe2x80x9d can take many different forms, some of which gives them the shape of a localized mechanical locking element, and others a more spread out shape. One designates here means which contribute to oppose any relative movement of the tire on the rim and which contribute to the security of the immobilization of the tire on its rim. Let us note also that the so-called xe2x80x9crelaxed naturalxe2x80x9d position of the securing means can be different from the one they have when they are engaged with the complementary bearing of the rim, the latter (engaged position) generally being an intermediate position between the relaxed natural position and the position stressed radially outward, in which those securing means are free of any engagement with the said complementary element.
According to one particular embodiment, said securing means include a locking element made in the form of a protuberance or groove, arranged on the radially inner face of the base axially at an intermediate position, said locking element having a predetermined height (H) measured parallel to a radius from the inner face of the base, and the said complementary bearing arranged on the rim being adapted to said locking element.
It is known that a tire generally comprises a crown part comprising a tread. The concept of the invention having been defined above, let us point out how said degree of flexibility can be adjusted (through the choice of materials and design) for an excellent operation of the invention. It is advisable that, when the tire is in a closed toroid configuration defining a tight chamber, a pressure reduction of the chamber produces the desired displacement of said locking element toward the larger radius before producing a deformation of the crown, the extent of which opposes said displacement of the base to the larger radius. It is therefore advisable, through a judicious sizing of the locking element and of the base supporting it, as well as through a judicious sizing of the crown part (the rigidity of which must be sufficient), for the increase in diameter of the locking element not to impose overly great stresses or, in any case, for the crown part to stand up well enough not to collapse. Preferably, it is desirable for what is stated above to remain true regardless of the degree of wear of the tire, so that demounting can take place under the same conditions as mounting. However, as will be seen below, some applications of the invention do not resort to a pressure reduction of the inner chamber of the tire. Consequently, this aspect is not universal.
From another aspect, the invention proposes a combined toroid tire and rim assembly, said rim coming in a single piece and said toroid tire including, seen in mounting position on a suitable rim:
two sidewalls;
a mounting base on the rim, said base forming a sleeve extending crosswise from each sidewall in the direction of the other sidewall, the radially inner ends of the sidewalls being extended by said base:
a crown part comprising the tread and joined to the radially upper end of the sidewalls, in which said base:
is capable of forming a closed toroid defining a tight chamber, complementing the sidewalls and the crown part, even when the tire is not mounted on the rim;
includes a concurrent locking part on the rim, situated axially between the sidewalls, said concurrent locking part presenting, in stress-free state, a minimum perimeter (Pm), the rim having a support area in the radial projection of said base, when the tire is considered in mounting position on the rim, said support area presenting a minimal (Pjm) opposite the portion of the concurrent locking part and, axially on at least one side of the part presenting the minimum perimeter (Pjm), an area presenting a maximum perimeter (PjM) greater than (Pjm) and capable of receiving the toroidal tire on the rim, the total rim situated on said side presenting a perimeter no greater than (PjM) in any axial position, said minimum perimeter (Pm) of the concurrent locking part being less than the maximum rim perimeter (PjM), said concurrent locking part being elastically extensible, so that, when the tire is in place on the rim, the concurrent locking part cooperates with the rim in opposing any relative movement of the tire in relation to the rim at least axially toward said side.
Several embodiments of the invention are described below, which can be classified in three families:
The first family uses tire casings of appearance identical or very close to the shape of the tire casings in current use on the priority date of this invention. They are tire casings which are hooked on the rim against a flange situated axially outside the rim. The ETRTO standards in force on the priority date of this invention should be consulted, for example, to get more precise information on the standardized shape of the corresponding tire casing and rim beads.
A second family uses a tire casing having the general appearance of a toroid split in its radially inner wall.
Finally, a third family uses the principle of a tubular tire: it involves a toroid-shaped tire containing a tight closed cavity obtained on molding of the tire.
The second and third families propose developing a tire casing or closed tubular tire, not currently available today. As for the first family, it enables the today existing tire casings to be used, adding to them a ring specifically developed to form, by combination with a standard tire casing, a tire having the mounting and demounting properties proposed in the present invention.
The invention therefore also extends to a ring designed to be mounted under the beads of a tire casing having a crown, two sidewalls each ending in a bead, in order to form, after mounting of the beads on the ring, a tire designed to be mounted on an adapted rim, said ring including two seats, each receiving a bead, and including securing means for axially opposing any relative movement of the tire on the rim in one of the two directions at least, said securing means being:
arranged on the radially inner face of the ring;
designed to cooperate with a complementary bearing arranged on the rim in order to oppose any relative movement between tire and rim axially in the said direction at least;
arranged in a part of the ring which presents a degree of flexibility between a relaxed natural position and a position radially stressed outward, in which those securing means are free of any engagement with the said complementary element, said part of the base and the securing means being so shaped and constituted that:
when said chamber is at the same pressure as the atmospheric pressure prevailing outside the chamber, the securing means are engaged with the complementary element, so that the tire will be automatically secured in said one direction at least on the rim,
the release of the securing means requiring subjecting the latter to the action of outside means serving to make said securing means take said position stressed radially outward.
As already explained above, the securing means can be a locking element taking the shape of a protuberance or groove, arranged on the radially inner face of the ring at a position axially separated from the seats, said locking element having a predetermined height (H) measured parallel to a radius from the inner face of the ring, the said complementary bearing arranged on the rim being adapted to said locking element. The remarks made above regarding the degree of flexibility are also applicable.
Through the choice of materials, design and sizing of the ring, it can very easily be given sufficient flexibility in the median part between the seats. There again and by comparison with the pliancy of the ring, the rigidity of the crown part must be sufficient for the reduction in pressure of the tire to produce an increase in diameter of the median part of the ring without the crown part collapsing.
In all the families, it is to be noted that the rim used is not tight or, more exactly, that it is the tire itself which has to be tight. Tightness is ensured between tire casing and ring in the first family and at the closure in the case of the second family (split toroidal tire). In other words, the air coming from the air chamber and that might have reached between the tire and the rim must be able to escape, so that there is no pressure build up between rim and mounting base. Such looseness of the rim can be obtained, for example, because the constituent material is porous, or because there are small vent holes judicially arranged, or because there are grooves correctly placed and oriented to the radially outer surface of the rim, or also because there are grooves correctly arranged and oriented to the radially inner surface of the mounting base. Other expedients can also be used, such as textile drains or a draining surface coating. Securing efficiency thereby does not change in time.
From another aspect, the invention proposes reducing the pressure of the inner cavity of a tire in order to increase in diameter or facilitate the increase in diameter of a portion of the mounting base, which makes it possible to fit the tire easily on the rim, the final securing of the tire on the rim being carried out by eliminating the vacuum.
This mounting by simple relative translation is done without prejudice to obtaining a securing in a strictly determined axial position. The invention therefore makes it possible to devise and carry out a secure fastening of the tire on its rim, while greatly simplifying mounting, compared to the known solutions which resort to a rim having a center mounting space, the minimum depth of which is dictated by the height of the rim flanges, as well as to a rim in several pieces, or to a previous insertion of the rim inside the beads with relative rotation of the planes of the rim and tire casing. For mounting of the tire on the rim as well as for demounting, the invention provides for reducing the pressure of the inner chamber of the tire during mounting and demounting. Outside of the mounting and demounting operation, the invention proposes a solution which, when the tire is at atmospheric pressures, makes sure of a retention of the tire on the rim that is as safe and positive as with the known solutions of the state of the art. In fact, at ambient atmospheric pressure, without express stresses (a vacuum in relation to ambient atmospheric pressure does not exist naturally), the tire cannot be demounted accidentally, while, in the case of passenger vehicle tire casings and their hollow-base rims, as ETRTO standardized on the priority date of the present application, in case of total deflation, it is not impossible that the bead or beads might be spontaneously engaged in the mounting groove and then pass over the rim flange (a phenomenon known as rolling off the rim).
The invention thus extends to a method of mounting on a rim of a closed toroidal tire forming a tight chamber, said tire including:
a rim mounting base, said base forming a sleeve intended to rest on said rim in mounting position;
securing means for axially opposing any relative movement of the tire on the rim in one of the two directions at least, said securing means being:
arranged on the radially inner face of the base;
designed to cooperate with a complementary bearing arranged on the rim in order to oppose any relative movement between tire and rim axially in the said direction at least;
arranged in a part of the ring which presents a degree of flexibility between a secured position and a radially outermost unsecured position;
said method including the following steps:
when the tire is in a closed toroidal configuration defining a tight chamber, reducing the pressure of the chamber until producing a sufficient displacement of the securing means toward the larger radius;
fitting or completing the fitting of said tire on said rim until it takes its final axial position relative to the rim;
eliminating the vacuum so that the securing means are displaced toward the smaller radius.
The invention also concerns a method of demounting off the rim of a closed toroidal tire forming a tight chamber, said tire including:
a rim mounting base, said base forming a sleeve intended to rest on said rim in mounting position;
securing means for axially opposing any relative movement of the tire on the rim in one of the two directions at least, said securing means being:
arranged on the radially inner face of the base;
designed to cooperate with a complementary bearing arranged on the rim in order to oppose any relative movement between tire and rim axially in the said direction at least,
arranged in a part of the ring which presents a degree of flexibility between a secured position and a radially outermost unsecured position;
said method including the following steps:
creating a greater pressure acting on the tire between rim and tire than the pressure prevailing in the tight chamber, in order to produce a sufficient displacement of the securing means toward the larger radius;
removing said tire from said rim by sliding it axially.
In an advantageous use of the demounting method, in order to create a greater pressure between rim and tire than in the tight chamber, the pressure in said chamber is reduced, while the tire floats outside at atmospheric pressure. As a variant, in order to obtain a difference in pressure on both sides of the mounting base, instead of lowering the pressure prevailing in the tire chamber under atmospheric pressure, a fluid can also be injected under pressure between the rim and the mounting base, ideally in a place close to the securing means, which can be done, for example, through a vent hole provided on the rim, as explained above. Said securing means can also be possibly mechanically stressed, that is, pushed radially, in addition to or in place of a reduction of the pressure prevailing in the tire chamber. The methods of mounting and demounting described above propose a step in the course of which the toroidal tire slides by simple axial movement relative to the rim, without requiring a bead of a tire casing to be engaged in a mounting groove; these methods prove interesting and have broader applications than in connection with a tire according to the invention; for example, in case the tire should be well secured axially in relation to the rim, it is still necessary to perfect securing by creating a hooping or increasing the hooping of the base on the rim through inflation of the tire chamber; the fact of stressing said securing means radially toward the wider radii contributes to the relative axial movement between base and rim.
The invention will be better understood by the description to follow of several non-imitative examples, and by reference to the attached drawings: